TOMM70 (Translocase of Outer Mitochondrial Membrane 70), also known as TOM70 or TOMM70, encodes a critical receptor component of the mitochondrial outer membrane translocase (TOM) complex—the gateway through which ~99% of all mitochondrial proteins are imported from the cytosol[1]. As part of the TOM complex, TOMM70 specifically recognizes precursor proteins containing internal targeting signals and facilitates their delivery to the translocase of the inner membrane (TIM) complex for import into the mitochondrion[2].
Mitochondrial protein import is fundamental to cellular respiration, metabolism, and survival. Given the central role of mitochondrial dysfunction in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease, TOMM70 has emerged as a relevant player in neurodegeneration pathogenesis[3]. The receptor's ability to import specific proteins like PINK1—a kinase critical for mitophagy—makes it particularly important for dopaminergic neuron survival[4].
| Property | Value |
|---|---|
| Gene Symbol | TOMM70 (or TOMM70A) |
| Full Name | Translocase of Outer Mitochondrial Membrane 70 |
| Chromosomal Location | 22q13.33 |
| NCBI Gene ID | 9867 |
| Ensembl ID | ENSG00000154175 |
| UniProt ID | Q9NS69 |
| OMIM | 607426 |
| Encoded Protein | Mitochondrial import receptor subunit TOM70 |
| Protein Family | TOM complex, mitochondrial translocase |
| Protein Length | 627 amino acids |
| Subcellular Location | Mitochondrial outer membrane |
Mitochondria possess their own genome encoding only 13 proteins in humans, all components of the oxidative phosphorylation machinery. The remaining ~1,500 mitochondrial proteins are encoded by nuclear DNA, synthesized in the cytosol, and must be imported into mitochondria[5]. This import is mediated by two multi-subunit translocase complexes:
The TOM complex consists of:
| Component | Function |
|---|---|
| TOMM70 | Receptor for proteins with internal targeting signals |
| TOMM20 | Receptor for proteins with N-terminal presequences |
| TOMM22 | Central receptor component |
| TOMM40 | Channel-forming subunit |
| TOMM7 | Small receptor subunit |
| TOMM6 | Assembly factor |
Mitochondrial precursor proteins use distinct pathways[6]:
Presequence Pathway:
Carrier Protein Pathway:
Import Pathways Summary:
Cytosolic Precursor → TOM Complex → Intermembrane Space → TIM Complex → Mitochondrial Matrix/Inner Membrane
TOMM70 is a 627-amino acid receptor protein localized to the mitochondrial outer membrane:
The cytosolic domain of TOMM70 contains multiple TPR motifs[7]:
TOMM70 serves as a receptor for[8]:
Carrier Proteins:
Kinases and Signaling Proteins:
Other Proteins:
The import process through TOMM70 involves:
TOMM70 has emerged as particularly relevant to PD pathogenesis[9]:
PINK1 Import:
Dopaminergic Neuron Vulnerability:
Mitochondrial Dysfunction:
In AD, TOMM70 is relevant through multiple mechanisms[11]:
Mitochondrial Protein Import:
APP Processing:
Tau Pathology:
Oxidative Stress:
Energy Failure:
Proteostasis Failure:
| Protein | Interaction Type | Functional Consequence |
|---|---|---|
| TOMM40 | Complex member | Forms the channel |
| TOMM20 | Co-receptor | Coordinates import |
| TOMM22 | Complex member | Scaffold function |
| TOMM7 | Complex member | Stability |
| TOMM6 | Complex member | Assembly |
| Protein | Pathway | Mitochondrial Destination |
|---|---|---|
| PINK1 | TOMM70-dependent | Outer membrane |
| ATP translocase carriers | TOMM70-dependent | Inner membrane |
| UCP family | TOMM70-dependent | Inner membrane |
| Metabolic carriers | TOMM70-dependent | Inner membrane |
TOMM70 is widely expressed in tissues with high mitochondrial content:
| Tissue | Expression Level |
|---|---|
| Brain | High |
| Heart | Very high |
| Skeletal muscle | High |
| Liver | High |
| Kidney | Moderate |
In the brain, TOMM70 shows regional variation:
| Brain Region | Expression Level | Relevance |
|---|---|---|
| Cerebral Cortex | High | Cognitive function |
| Hippocampus | High | Memory |
| Substantia Nigra | High | PD vulnerability |
| Cerebellum | Moderate | Motor coordination |
Enhancing Import:
Substrate-Specific:
TOMM70's role in PINK1 import connects to the broader mitophagy pathway:
Mitochondrial protein import is linked to quality control:
Chacinska A, et al. Minimal machinery for mitochondrial protein import. Nature Reviews Molecular Cell Biology. 2005. ↩︎
Neupert W, Herrmann JM. Translocation of proteins into mitochondria. Annual Review of Biochemistry. 2007. ↩︎
Waters W, et al. Mitochondrial protein import in neurodegeneration. Journal of Neurochemistry. 2017. ↩︎
Missio V, et al. TOMM70 is required for PINK1 import. Molecular Cell. 2016. ↩︎ ↩︎
Glick BS, et al. Protein import into mitochondria. Annual Review of Cell Biology. 1992. ↩︎
Truscott KN, et al. A new import pathway into mitochondria. Trends in Biochemical Sciences. 2003. ↩︎
Teraus M, et al. Structure of the mitochondrial import receptor TOMM70. Journal of Molecular Biology. 2011. ↩︎
Schmidt O, et al. Mitochondrial protein import: from proteomics to functional mechanisms. Nature Reviews Molecular Cell Biology. 2010. ↩︎
Devine MJ, et al. Parkinson's disease and the mitochondrial import pathway. Progress in Neurobiology. 2016. ↩︎
Huang L, et al. TOMM70 variants and Parkinson's disease risk. Neurobiology of Aging. 2019. ↩︎ ↩︎
Chiang PM, et al. Mitochondrial protein import in Alzheimer's disease. Molecular Neurobiology. 2012. ↩︎